Why did you buy a new car?

And so on, until suddenly you're reliving a painful memory in front of a 4-year-old boy. Who will then report, with frightening attention to detail, the complete story to the rest of the family.

So my wife and I have to be careful when talking about recent news, such as the senseless murder of Officer Gary Skerski. Because if our son hears about "the cop who got shot," he'll ask, Why was that police officer shot? And if he follows his usual line of questioning backwards, he'll arrive at the same question many of us have been asking ourselves for the past week and a half:

Why do people shoot each other?

Especially, as of late, in Philadelphia?

OK, maybe it's just a statistical quirk. Maybe by New Year's Eve, we'll look back and realize that just as many people were shot as last year. Maybe we're paying closer attention now because we all see, in our fevered imaginations, the image of a hero cop trying to save a frightened, innocent woman with a burly arm around her neck. And with a twitch of the trigger, the hero cop—a father, a husband—is gone.

We also see the two brothers, 13 and 14 years old, cradling their assault rifles and sawed-off shotguns as they sleep.

We see a pregnant mother, shot in the back on Mother's Day.

We see commuters kissing pavement when gunfire breaks out on a SEPTA platform in University City.

And we ask ourselves the same thing my son would:

Why do people shoot each other?

There's one answer I could give him: There are too many guns on the street. Only, that's not quite it. I've read a bunch of op-eds and news stories about how restricting gun sales would be one way to dampen the pops of gunfire in our neighborhoods. But would a monthly limit put the smallest of dents in the black market? It would probably have the opposite effect. There's a Don Winslow novel where one character, a drug dealer, actually prays for federal bans and restrictions. "Oxygen," he says. "I wish the government would outlaw oxygen."

Beyond that, it is not the semiautos; it is the people holding the semiautos. The people in this city who think the right answer is to pick up their piece and start blasting.

Which brings us back to:

Why do people shoot each other?

Maybe it's not even the concept of people shooting each other that would be tough to explain to my son. The world is full of bad people who do bad things to each other. I think he understands that. Maybe it's the idea of guns.

Every object he knows has a purpose. Books are to be read. Toy cars, pushed.

But guns? They are meant to fire projectiles that skewer flesh, muscle and bone. Or break the skin, then explode out. Or remove a body part entirely. How do you explain why people felt the need to invent this kind of thing?

Just a few days ago, we were at a relative's house. An older cousin was playing a computer game—Quake III, where the screen is dominated by an obnoxiously large weapon that bounces and twitches and blasts away at everything else on the screen that dares move. I saw my son first. His eyes were wide. Then I saw what he was looking at. My heart went cold. I took him by the hand and led him outside to play before he had a chance to ask the words:

Why do people shoot each other?

But someday—and I'm very worried about that day—there's going to be a shooting and he's going to hear about it, or catch a snippet of a news report about it. I'll have to explain it to him. Why people shoot each other.

Do any of you have a good answer?